Pretty much every day that I comment on HN, at least a couple of the comments I write get to +3 or so by the end of the day, and then in the middle of the night

Pretty much every day that I comment on HN, at least a couple of the comments I write get to +3 or so by the end of the day, and then in the middle of the night they're at +1 or 0. Consistently. I assume it's this.